Faqs Biology And Human Welfare Class 12 Biology Cbse And Chse

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🦠 FAQs: Biology and Human Welfare Class 12 Biology

Short and Long Questions and answers from the chapter Biology and Human Welfare Class 12 Biology for CBSE and CHSE Board Exam given below

I. Human Health and Disease

Q1. What is the difference between an innate and acquired immune response?

Innate Immunity: Non-specific defense present at the time of birth. It includes physical barriers (skin, mucus coating), physiological barriers (stomach acid, tears), cellular barriers (macrophages), and cytokine barriers (interferons).

Acquired Immunity: Pathogen-specific defense acquired after birth. It involves memory and the production of antibodies by B-lymphocytes (humoral immunity) and T-lymphocytes (cell-mediated immunity).

Q2. Explain the difference between primary and secondary lymphoid organs.

Primary Lymphoid Organs: Sites where lymphocytes mature and differentiate into antigen-sensitive cells (e.g., Bone Marrow for B-cell maturation and Thymus for T-cell maturation).

Secondary Lymphoid Organs: Sites where mature lymphocytes interact with antigens to generate an immune response (e.g., Spleen, Lymph Nodes, Tonsils, Peyer's Patches).

Q3. Differentiate between active and passive immunity, with examples.

Active Immunity: The host's own body produces antibodies in response to antigen exposure. It is slow but provides long-lasting memory.

Example: Infection, or Vaccination (introducing weakened or inactive pathogen/antigen).

Passive Immunity: Readymade antibodies are directly given to the host. It is fast but provides no memory and is short-lived.

Example: Transfer of IgA antibodies from mother to infant through colostrum (first milk), or administering anti-venom (containing pre-formed antibodies).

Q4. Name the causative agents and modes of transmission for AIDS and Cancer.

AIDS (Acquired Immuno Deficiency Syndrome):

Causative Agent: HIV (Human Immunodeficiency Virus).

Transmission: Sexual contact, contaminated blood and blood products, sharing infected needles (IV drug users), and from infected mother to child via placenta.

Cancer (Malignancy):

Causative Agents (Various): Oncogenic viruses (e.g., HPV), Physical agents (X-rays, UV radiation), Chemical agents (nicotine in tobacco smoke).

Transmission: Not transmitted from person to person (Non-infectious disease).

Q5. What is the principle of vaccination/immunisation?

A. The principle is based on the memory of the immune system. A preparation of inactivated/attenuated (weakened) pathogens, or their antigenic proteins, is introduced into the body. This stimulates the production of memory B and T-cells. If the real pathogen attacks later, the memory cells quickly mount a massive secondary immune response to eliminate the infection.

II. Microbes in Human Welfare

Q6. Give four examples of microbes used in household products.

Lactobacillus (LAB - Lactic Acid Bacteria): Converts milk into curd by producing lactic acid, which partially digests milk proteins.

Saccharomyces cerevisiae (Brewer's Yeast): Used in baking bread and producing alcoholic beverages (fermentation).

Propionibacterium shermanii: Used to produce the large holes (due to CO2 production) in Swiss cheese.

Penicillium roqueforti and Penicillium camemberti: Used to ripen and flavour different varieties of cheese.

Q7. What is the role of microbes in sewage treatment (STP)?

A. In the secondary treatment of sewage, aerobic microbes (like Aerobacter and Bacillus) are introduced.

They form flocs (masses of bacteria associated with fungal filaments).

The microbes vigorously grow and consume the major part of the organic matter in the effluent, reducing its BOD (Biological Oxygen Demand).

A lower BOD indicates less polluting potential.

Q8. Name two bioactive molecules produced by microbes and their use.

Cyclosporin A: Produced by the fungus Trichoderma polysporum. It is used as an immunosuppressive agent in organ transplant patients.

Statins: Produced by the yeast Monascus purpureus. They act as blood cholesterol-lowering agents by inhibiting the enzyme responsible for cholesterol synthesis.

Q9. How are microbes used as biofertilizers? Name three types.

A. Biofertilizers are organisms that enrich the nutrient quality of the soil. They are used to reduce reliance on chemical fertilizers.

Bacteria (e.g., Rhizobium): Forms nodules on the roots of leguminous plants and fixes atmospheric nitrogen into usable forms.

Cyanobacteria (e.g., Anabaena, Nostoc): Autotrophic microbes that fix atmospheric nitrogen in paddy fields.

Fungi (e.g., Glomus species): Forms Mycorrhiza (symbiotic association with plant roots) and helps the plant absorb phosphorus from the soil.

III. Strategies for Enhancement in Food Production

Q10. What is single-cell protein (SCP) and why is it important?

A. Single-Cell Protein (SCP) refers to the protein-rich biomass of microbes (e.g., Spirulina, yeast, Methylophilus methylotrophus) grown on industrial scale.

Importance: It is a cheap, rich, and high-quality source of protein, minerals, fats, and vitamins. It helps address the growing gap between food supply (especially protein) and the rapid population growth.

Q11. Define Inbreeding and Outbreeding. State the disadvantage of continuous inbreeding. A.

Inbreeding: Mating between animals of the same breed for 4-6 generations. It increases homozygosity and eliminates less desirable genes.

Outbreeding: Breeding of unrelated animals, which includes: Out-crossing (same breed, no common ancestor for 4-6 generations), Cross-breeding (different breeds), and Interspecific hybridisation (different species).

Disadvantage of Continuous Inbreeding (Inbreeding Depression): Leads to reduced fertility and productivity. This condition requires selected animals of the breeding population to be mated with unrelated superior animals of the same breed (out-crossing) to restore vigour.

Q12. What is Somatic Hybridisation?

A. Somatic hybridisation is a method of producing hybrid plants by the fusion of protoplasts (plant cells without cell walls) isolated from two different varieties or species.

Example: Pomato, a hybrid of potato and tomato, was created using this technique, although it lacked commercial value.

Q13. Briefly explain the concept of Biofortification.

A. Biofortification is the process of breeding crops with higher levels of vitamins, minerals, protein, and healthier fats to improve public health.

Example: High protein content in beans, iron-enriched rice, and Vitamin A-enriched carrots. The Indian Agricultural Research Institute (IARI) has released several biofortified vegetable crops.

Long Question FAQs: Biology and Human Welfare

Q1. Describe the different types of barriers that constitute the innate immune system of the human body.

A. Innate immunity is the non-specific defense mechanism present at the time of birth, providing the first line of defense. It consists of four main types of barriers:

Physical Barriers:

Skin: The principal barrier that prevents the entry of most microorganisms.

Mucus Coating: The mucous membrane lining the respiratory, gastrointestinal, and urogenital tracts traps microbes entering the body.

Physiological Barriers:

Acid in the Stomach (HCl): Kills most pathogens ingested with food.

Saliva in the Mouth: Contains lysozyme, which is antibacterial.

Tears from the Eyes: Also contain lysozyme, which prevents eye infections.

Cellular Barriers:

Certain types of leukocytes (white blood cells) act as cellular barriers.

Phagocytes: Cells like polymorphonuclear leukocytes (PMNLs) (neutrophils) and monocytes (which differentiate into macrophages) actively engulf and destroy microbes.

Natural Killer (NK) cells: A type of lymphocyte that detects and destroys virally infected cells and some tumor cells.

Cytokine Barriers:

These are proteins secreted by specific cells in response to infection.

Interferons: Viral-infected cells secrete proteins called interferons (a type of cytokine). These protect non-infected cells from further viral infection by interfering with viral replication.

Q2. Explain the difference between primary and secondary immune responses. How does vaccination utilise this difference?

A. The immune system mounts two types of responses upon encountering an antigen:

Feature	Primary Immune Response	Secondary/Anamnestic Immune Response
Occurrence	Occurs upon the first encounter with a specific antigen/pathogen.	Occurs upon subsequent encounters with the same antigen/pathogen.
Speed	Slow (takes time to generate an antibody-producing clone).	Rapid and massive (due to the presence of memory cells).
Magnitude	Low intensity (less antibody produced).	High intensity (much larger quantity of antibodies produced).
Duration	Short-lived.	Long-lasting and provides protection.
Key Cells	Primarily involves the activation of naïve B and T cells.	Primarily involves the activation of memory B and T cells.

Role of Vaccination:

Principle: Vaccination is based on the phenomenon of the secondary immune response.

Mechanism: A vaccine contains a preparation of inactivated pathogen, attenuated (weakened) pathogen, or antigenic proteins.

The primary exposure to this antigen (vaccine) stimulates the immune system to produce antibodies and generates memory B and T-cells.

When the vaccinated individual encounters the actual pathogen (natural infection), the existing memory cells rapidly recognize the antigen and mount a powerful, fast-acting secondary immune response, neutralizing the pathogen before it can cause disease.

Q3. Describe the role of microbes in the secondary treatment (Biological Treatment) of sewage in a Sewage Treatment Plant (STP).

A. Sewage (municipal waste water) contains large amounts of organic matter and pathogenic microbes. Secondary treatment is crucial to reduce the pollutants before the water is released into natural bodies.

Procedure:

Primary Effluent Transfer: The effluent (liquid) from the primary settling tank (where solid waste is removed) is pumped into large aeration tanks.

Aeration and Floc Formation:

The effluent is constantly agitated mechanically and air is pumped into the tank.

This vigorous agitation encourages the rapid growth of useful aerobic microbes into flocs.

Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.

BOD Reduction:

The aerobic microbes in the flocs consume the major part of the organic matter present in the effluent.

This consumption significantly reduces the Biological Oxygen Demand (BOD) of the effluent. BOD is the amount of oxygen required by the microbes to oxidize all the organic matter in one litre of water. A lower BOD indicates less pollution.

Settling and Activated Sludge:

Once the BOD is reduced significantly (as monitored by testing), the effluent is pumped to a settling tank.

The bacterial flocs settle down, forming the activated sludge.

Inoculum and Anaerobic Digestion:

A small part of the activated sludge is pumped back into the aeration tank to serve as an inoculum (starter) for the next cycle.

The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters, where anaerobic bacteria digest the bacteria and fungi in the sludge, producing a mixture of gases like methane, H2S, and CO2 (biogas).

Q4. Explain the process of 'Inbreeding' in animal husbandry, state its benefits, and describe the disadvantage it carries.

A. In animal breeding, controlled mating is used to improve the quality of livestock.

Inbreeding:

Definition: It is the mating of more closely related individuals within the same breed for 4-6 generations.

Strategy: Superior males and superior females of the same breed are identified and mated. The progeny are then evaluated, and the superior ones are identified for further mating.

Benefits of Inbreeding:

Increased Homozygosity: It exposes recessive, undesirable genes that are otherwise masked by dominant genes. These undesirable genes can then be eliminated by selection.

Pure Lines: It helps in the accumulation of superior genes (genes for high milk yield, high growth rate) and the creation of a pure line (homozygous genes for the desired trait).

Selecting Superior Animals: It helps in selecting animals that are better than the others in the population, particularly for a specific trait, for further breeding.

Disadvantage (Inbreeding Depression):

Cause: Continuous and intensive inbreeding, especially for many generations, usually reduces the fertility and productivity of the animals.

Cure: This loss of vigour is called inbreeding depression. To overcome it, the selected animals of the breeding population should be mated with unrelated superior animals of the same breed (out-crossing) once every few generations.

Q5. Describe the significance of Biofortification and Single-Cell Protein (SCP) in addressing global nutritional challenges.

A. Biotechnology and modern breeding practices provide important solutions to combat hidden hunger (deficiencies in micronutrients) and protein malnutrition.

I. Biofortification:

Definition: It is the method of breeding crops to have higher levels of vitamins, minerals, protein, and healthier fats than existing varieties.

Significance:

Combats Hidden Hunger: It is the most practical and inexpensive way to improve the health of vast populations suffering from micronutrient deficiencies (like iron, iodine, Vitamin A) by targeting the staple crops they already consume.

Examples: High protein maize (twice the amount of amino acids), iron-fortified rice (five times more iron), and Vitamin A-enriched carrots and spinach.

II. Single-Cell Protein (SCP):

Definition: The protein-rich microbial biomass (e.g., bacteria, algae, fungi) produced on an industrial scale using cheap substrates (like waste water, molasses, wood pulp) to serve as a food supplement for humans or feed for animals.

Significance:

Addresses Protein Gap: With a rapidly growing global population, SCP offers a cheap, large-scale, and sustainable source of protein that can bridge the demand-supply gap.

Example (Spirulina): The algae Spirulina is grown easily on waste water from potato processing plants. It is rich in protein, minerals, fats, and vitamins, and can be used as food.

Environmental Benefit: The process utilizes and converts agricultural, industrial, or municipal wastes into high-value protein, helping to reduce pollution.

Q6. Define drug abuse and list the major categories of drugs commonly abused. Explain the concept of dependence and how youth can be prevented from engaging in drug abuse.

A. Drug Abuse refers to the consumption of drugs (e.g., narcotics, psychedelics, psychotropics) for purposes other than their therapeutic/medical use, in amounts or frequencies that impair an individual's physical, psychological, or physiological functions.

Major Categories of Abused Drugs:

Opioids: Bind to opioid receptors in the CNS and gastrointestinal tract. Example: Heroin (smack) is chemically diacetylmorphine, obtained from the latex of the opium poppy (Papaver somniferum). It is a depressant.

Cannabinoids: Interact with cannabinoid receptors primarily in the brain. Example: Marijuana, Hashish, Ganja, Charas, obtained from the inflorescences of the Cannabis sativa plant. They affect the cardiovascular system.

Cocaine (Coca Alkaloids): Obtained from the coca plant (Erythroxylum coca). It acts as a powerful stimulant on the Central Nervous System (CNS) and interferes with the transport of the neurotransmitter dopamine.

Dependence:

Dependence is the tendency of the body to manifest an unpleasant withdrawal syndrome if the regular dose of the drug/alcohol is abruptly discontinued.

This syndrome is often characterized by anxiety, restlessness, nausea, and tremors. Dependence drives the user to take the substance even when it is not needed, often leading to addiction.

Prevention and Control in Youth:

Avoid Undue Pressure: Parents and teachers should identify and avoid pushing children towards unrealistic expectations, which can lead to stress and drug use.

Education and Counselling: Educating students about the dangers, addictive nature, and irreversible harm of substance abuse is crucial.

Seeking Help: Encourage children to seek professional help from psychologists or counselors if they are dealing with problems or peer pressure.

Parental Role: Parents should monitor their child's friend circles and provide a loving and secure environment to deter them from falling into drug use.

Q7. Explain the process of Biogas production using a biogas plant, highlighting the significance of methanogens in this process.

A. Biogas is a mixture of gases containing predominantly methane (CH)4along with CO2 and H2S, produced by the anaerobic decomposition of organic material (animal dung, agricultural waste).

Biogas Plant Structure and Process:

Digester Tank: A concrete tank (10-15 feet deep) where the raw materials are fed.

Slurry Preparation: Cow dung (or biomass) is mixed with water to create a thick slurry in the mixing tank and fed into the digester.

Anaerobic Digestion: The decomposition occurs in three stages inside the tank under anaerobic conditions (in the absence of oxygen):

Solubilisation/Hydrolysis: Extracellular enzymes break down complex polymers (cellulose, proteins) into simple monomers (sugars, amino acids).

Acidogenesis: Facultative and obligate anaerobic bacteria convert these monomers into organic acids (like acetic acid).

Methanogenesis: This is the critical final step. Specific anaerobic bacteria called Methanogens (e.g., Methanobacterium) act on the organic acids (e.g., acetic acid) and convert them into methane (CH4) and carbon dioxide (CO2).

Gas Collection: The biogas produced is collected in the gas holder/collecting tank placed over the digester. An outlet pipe leads the gas to the points of use.

Spent Slurry: The effluent (spent slurry) is removed from the outlet and used as a rich biofertilizer because it still contains mineral nutrients.

Significance of Methanogens:

Methanogens are strictly anaerobic bacteria.

They are responsible for the final and most important step of converting acetic acid and other simple compounds into methane (the main component of biogas).

They are commonly found in the rumen (part of the stomach) of cattle and in anaerobic sludge during sewage treatment.

Q8. Outline the various steps involved in plant breeding for developing a new crop variety.

A. Plant breeding is the purposeful manipulation of plant species to create desired plant types that are better suited for cultivation, yield, and disease resistance. The main steps are:

Collection of Variability:

Gathering and collecting all the different alleles (genes) for various traits present in a population.

The entire collection of all the diverse alleles of a gene or genes in a given crop is called the germplasm collection.

Evaluation and Selection of Parents:

The collected germplasm is screened for desirable traits.

Only the plants that are identified as having the desired traits are selected to be the parents in the breeding programme.

Cross-Hybridisation Among Selected Parents:

Hybridisation is performed to combine the desirable traits from two different plants (e.g., disease resistance from one, high yield from another).

Pollen from the plant with the desirable male trait is dusted onto the stigma of the plant selected as the female parent.

Selection and Testing of Superior Recombinants:

The hybrid progeny generated from the cross are evaluated.

Plants that have the best combination of desirable characters (superior recombinants) are selected. These selected plants are self-pollinated for several generations until they reach a state of uniformity (homozygosity).

Testing, Release, and Commercialisation of New Cultivars:

The newly selected line is tested for its performance (yield, resistance) under ideal conditions in research fields, followed by testing in farmer's fields at multiple locations for at least three growing seasons.

If the new variety is found to be superior to the existing control variety, it is released as a new cultivar (variety) for commercial cultivation.

Q9. Explain the adverse effects of alcohol and drug abuse on the human body, focusing on addiction and withdrawal.

A. Chronic use of drugs and alcohol has severe physiological, psychological, and social consequences.

Adverse Effects on the Body:

Physiological Damage:

Liver: Chronic use of alcohol leads to cirrhosis (fibrosis and damage) and fatty liver syndrome.

CNS: Affects the central nervous system, leading to impaired judgment, loss of control, depression, and memory loss. Opioids are depressants, while cocaine is a powerful stimulant.

Other Systems: Heavy drinking damages the heart (cardiomyopathy) and other vital organs.

Addiction and Dependence:

Addiction: A psychological attachment to the effects of drugs/alcohol.

Dependence: A physical state where the body needs the substance to function "normally." Abrupt cessation leads to withdrawal syndrome (anxiety, shaking, nausea), which drives the user back to the substance.

Intravenous Drug Use Risks: IV drug abusers who share needles risk transmitting severe infections like AIDS (HIV) and Hepatitis B, which are life-threatening and incurable.

Social and Psychological Effects:

Causes reckless behaviour, violence, and vandalism.

Leads to a decline in academic performance, social isolation, and withdrawal from family and friends.

Can lead to financial distress, marital problems, and a breakdown of the social fabric.

Q10. What is the significance of 'Selection and Selfing' in plant breeding? Briefly describe the advanced animal breeding techniques of Artificial Insemination (AI) and Multiple Ovulation Embryo Transfer Technology (MOET).

Significance of Selection and Selfing in Plant Breeding:

After the cross-hybridisation of selected parents, the progeny contain a mixture of genes (recombinants).

Selection: The superior recombinants (those with the desired trait combination) are selected.

Selfing (Self-pollination): The selected superior plants are self-pollinated for several generations.

Goal: This continuous selfing leads to a state of homozygosity (a pure line). Once the line becomes homozygous, the desirable traits will no longer segregate, ensuring that the new variety breeds true and maintains its superiority when released for commercial use.

Advanced Animal Breeding Techniques:

Artificial Insemination (AI):

Principle: The semen from a carefully selected superior male is collected and introduced into the reproductive tract of the selected female by the breeder.

Advantages: It overcomes the problem of distance and size/physical disability of the male. Semen can be frozen and stored for years (cryopreservation) and used to inseminate a large number of females, effectively increasing the reach of a superior sire.

Multiple Ovulation Embryo Transfer Technology (MOET):

Goal: To increase the herd size in a short time, especially of high milk-yielding cows or high-quality meat-producing bulls.

Procedure:

Hormone Administration: A high-yielding cow is administered FSH-like hormones to induce follicular maturation and super-ovulation (producing 6-8 eggs instead of one).

Artificial Insemination: The cow is either naturally mated with a superior bull or artificially inseminated.

Embryo Recovery: The embryos, usually at the 8-32 cell stage, are non-surgically recovered from the genetic mother.

Transfer: The embryos are transferred to surrogate mothers (recipient cows).

Result: The genetic mother is available for another round of super-ovulation, and the surrogate mothers carry the valuable calf to term.

Q11. Explain the concept of biocontrol agents and describe the role of different microbes used as biocontrol agents in integrated pest management (IPM).

A. Biocontrol Agents are the biological methods of controlling plant diseases and pests using natural predators, parasites, or pathogens, instead of chemical pesticides. This approach forms a key part of Integrated Pest Management (IPM).

Role of Microbes as Biocontrol Agents:

Fungus (Trichoderma):

Trichoderma species are free-living fungi commonly found in the root ecosystems.

They are effective biocontrol agents against several plant pathogens (fungal diseases).

They are useful for treating plant roots to protect them from disease.

Bacteria (Bacillus thuringiensis - Bt):

The spores of the bacterium Bacillus thuringiensis (Bt) are mixed in water and sprayed onto vulnerable plants (like Brassicas).

The spores are eaten by insect larvae, and the released toxin kills them.

This is highly specific and safe for other beneficial insects. It is available in sachets as a dried spore formulation.

Virus (Baculoviruses):

These are pathogens that attack insects and other arthropods. The genus Nucleopolyhedrovirus is a prime example.

They are excellent candidates for species-specific, narrow-spectrum insecticidal applications.

They show no negative impact on plants, mammals, birds, fish, or non-target insects, making them ideal for IPM.

Integrated Pest Management (IPM):

IPM is a system that employs a combination of methods, including biocontrol agents, to manage pests, aiming to reduce the use of chemicals while minimizing harm to the environment and non-target organisms.